Brown, who will turn 72 next month, is the only serious Democratic contender. His ability to raise money and gain endorsements frightened away other Democrats, including San Francisco Mayor Gavin Newsom.

After the June primary, Brown will face of one of two wealthy Silicon Valley Republicans in the general election: former eBay CEO Meg Whitman, a billionaire, or state Insurance Commissioner Steve Poizner, who also became a multimillionaire as a high-tech entrepreneur.

Brown says only someone with a long political resume such as his has the experience to solve California's ongoing fiscal crisis and its many other problems, from the quality of its public schools to the neglect of its state park system.

"What we need is not a scripted plan cooked up by consultants or mere ambition to be governor," he said in his Web cast, taking an apparent shot at Whitman. "We need someone with insider's knowledge but an outsider's mind, a leader who can pull people together. ... And at this stage in my life, I'm prepared to focus on nothing else but fixing this state I love."

Brown has frustrated his fellow Democrats for months while playing a wait-and-see game in the governor's race. All the while, he was raising nearly $12 million for a campaign while lining up support from deep-pocketed unions, celebrities and business leaders.

Without a challenger in the June primary, Brown has not had to campaign. In the meantime, two independent Democratic groups have emerged to fund an attack campaign against his Republican rivals, especially Whitman.

One, called Level the Playing Field 2010 Against Billionaire Meg Whitman for Governor, has started running radio commercials funded by unions representing nurses, teachers and painters. Another, the California Accountability Project, is funded by the Democratic Governors Association and has begun targeting Whitman's corporate background.

As independent committees, those groups can raise unlimited amounts of cash. Democrats say they will need to spend big this year because both Republicans challenging for that party's nomination have tens of millions of dollars at their disposal.

Whitman already has given her campaign $39 million from her personal fortune and has said she is willing to spend more than $100 million. Poizner has given his campaign $19 million and on Tuesday launched his first television commercial.

Brown will rely not only on dependable Democratic supporters but also on his political pedigree.

His experience in statewide office dates to 1970, when he was elected secretary of state. He won the first of his two terms as governor four years later, becoming California's youngest chief executive at age 36.

Brown's roots in California politics are even deeper. His father, Edmund G. Brown, served two terms as governor starting in 1959. His sister, Kathleen, served one term as state treasurer in the 1990s.

He ran three times for the Democratic Party's nomination for president and once for U.S. Senate, then served as the state party chairman in the early 1990s before reinventing himself as the tough-on-crime, pro-development mayor of Oakland. He served two terms before returning to statewide office as attorney general in 2006.

Outside California, Brown is best known for his unorthodox style.

As governor, he chose to live in a $250-a-month apartment instead of the newly built governor's mansion and was given the nickname "Governor Moonbeam" after proposing that California deploy communications satellites into space.

He left politics for a time to study Zen Buddhism in Japan and minister to the ill with Mother Teresa in India.

Brown often has referred to his long journey through life and says that's what best equips him to lead the nation's most populous -- and perhaps most troubled -- state. In his Web cast, he promised "no more smoke and mirrors" or "puffy slogans and platitudes," a not-so-subtle reference to the rocky tenure of Gov. Arnold Schwarzenegger.